This invention relates generally to imaging systems, and more particularly, to methods and apparatus for retrospectively correcting for deficiencies in image quality of images from imaging systems.
At least one known PET transmission scan is acquired using a rotating source of dual-511 keV gamma rays, such as the Ge-68 rod sources implemented on imaging systems, such as a PET Advance™ system from General Electric Medical Systems, Waukesha, Wis. At least one known PET imaging system is commonly used in whole-body acquisition mode to acquire adjacent axial fields-of-view (AFOVs) with a small amount of overlap. The acquisition mode is a step-and-shoot style and not continuous bed motion over a 15 cm AFOV. Post-acquisition reconstruction is then performed and the images are placed into an imageset. This imageset can then be viewed in using an orthogonal reformat tool, which allows viewing of a whole-body study in a more intuitive manner than simply viewing the native transaxial slices. Image quality problems can occur when combining the discrete sets of images together when the images were acquired using a step-and-shoot imaging system with an extended axial FOV. For example, if a cradle performing the axial translation either drives along an axis that is not the scanner axis or has a “differential sag,” i.e. varying curvature of a cradle top as a function of the cradle extension, then the image can include discontinuities. These discontinuities can be seen in a coronal view of the images as horizontal lines or in a sagittal view of the images as a “saw tooth” type effect. Such discontinuities reduce the quality of the imageset and hence the clinical confidence in the study.